Transferring to the LA County Sheriff's Department (LASD) two years later, he rose through the ranks, earning his stripes in 1987, and making lieutenant in 1991.
[15] In early 2011, the FBI launched an undercover probe at the Men's Central Jail, to investigate allegations of corruption and abuse.
[16][17] The U.S. Department of Justice's civil rights division also launched a wide-scale pattern and practice investigation into allegations that Antelope Valley deputies discriminated against minority residents who receive government housing assistance.
[19] In September 2012, the Citizens’ Commission on Jail Violence issued a final report that is very critical of the Sheriff Department’s management, including Baca, Tanaka and other executive-level staff, accusing them of fostering a culture in which deputies beat and humiliated inmates, covered up misconduct and formed aggressive deputy cliques in the county jails.
[22] The report also noted that Tanaka had accepted campaign contributions from many department employees, furthering perceptions of patronage and favoritism in promotion and assignment decisions.
[22] On March 6, 2013, Tanaka announced that he would retire as the Undersheriff, effective August 1, 2013, during an ongoing federal probe conducted by the FBI into widespread allegations of abuse, misconduct and mismanagement in County jails.
[25] On May 13, 2015, Tanaka was indicted on federal conspiracy and obstruction charges in the ongoing Los Angeles County Men's Jail corruptions investigation.
[25] On April 6, 2016, Tanaka was convicted on conspiracy and obstruction of justice charges by a federal jury in a case presided over by U.S. District Judge Percy Anderson.
[27] "The criminal charges centered on allegations that in 2011 Tanaka orchestrated a scheme to derail the FBI's jail investigation by intimidating the lead agent in the case, pressuring deputies not to cooperate and concealing the whereabouts of an inmate who was working as a federal informant.
[29] On June 27, 2016, Tanaka was sentenced to five years in prison, for civil rights abuses inside the nation's largest urban jail system.
[30] Tanaka planned to file a motion to sidestep his August 1 jail surrender deadline, and remain out on bail while he appealed his conviction.